José Luis Danelón

Efecto de la propagación asexual y prolongación del período vegetativo de Morus alba en la producción de capullos de seda

A. Pelicano, M. Divo de Sesar, N. Zamuner, J. L. Danelon, and M. Yoshida. 2007. The effect of asexual propagation and persistence of the vegetative growth of Morus alba on silk cocoon production. Cien. Inv. Agr. 34 (2):81-89. The goal of this work was to establish an effi cient protocol for vegetative propagation of Morus alba. At the same time this study aimed to evaluate the infl uence of this propagation protocol on the feeding of the larvae of Bombyx f mori and crude silk production. Vegetatively propagated mulberry plants were transplanted to 4 L containers and treated with 15 g of fertilizer, N:P:K (15:15:15,), and/or 6-benzyladenine (5 mg·L -1 ) (Ck). In autumn and spring, leaves were used for the feeding of one cohort of third stage larvae. It was observed that 60% of the plants treated with Ck sprouted before the others, in July, and the rest in August. Although the fertilized plants (TF) and those fertilized and treated with 6-benzyladenine (TFCk) sprouted shortly before the control (T), the Ck treated plants were notably uniform and had more and larger leaves. In the TFCk treatment, the percentage of fi ber, insoluble in neutral detergent (FIND) free from ash, was minor (29.73%). The quality of the food was refl ected in the weight gain and in crude silk percentage. Although interaction between TF and Ck was not signifi cant, there were signifi cant differences between control plants (T) and those treated with TF, TCk and TFCk. In the autumn test, the TCk treatment negatively affected the larvae of B. mori. These larvae twisted, assiduously inducing intestine evacuation. This caused reduced food consumption, and it was a transitory effect, but that meant a lower fi nal weight. The results of this work are very promising and useful for massive production since a longer vegetative cycle for M. alba would allow a greater number of B. mori generations per year.

In vitro digestion of fresh alfalfa under different conditions of ruminal pH

BACKGROUND Relatively low ruminal pH values have been frequently registered in dairy cows grazing alfalfa, which can be involved in reducing feed digestion. An in vitro experiment was carried out to study the effect of ruminal pH (6.4, 6.1, 5.8 and 5.5) on the digestion of fresh alfalfa. RESULTS Decreasing the pH, in vitro gas production (ivGP) decreased (P < 0.05). The lowest ivGP was registered at pH 5.5 and it was product of a higher lag time and a lower digestion rate. Dry matter disappearance (DMD) was not affected by pH at 48 h (P > 0.05). Neutral detergent disappearance (NDFD) at 48 h decreased below pH 6.1. The NDFD was reduced by 62% at pH 5.5 with respect to results at pH 6.4 and 6.1 (where the highest DMD and NDFD were observed). CONCLUSION As expected, low rumen pH decreased alfalfa digestion. However, limits to ruminal digestion activity differed from those usually proposed for TMR diets. It is apparent that different relationships between rumen pH and NDFD exist when cows graze fresh alfalfa or grasses. Moreover, our results suggest the convenience to complement the data obtained through ivGP, DMD and NDFD. While ivGP and DMD seem to be more useful at early digestion times, NDFD may be a good predictor of final digestion.